This invention pertains fasteners, and more particularly fasteners which attach one object to another and present high prevailing torque and pulling force.
In the original conventional technology of fasteners employed to securely attach one object to another, such as for example one part to another in the case of an automobile or an appliance, has utilized a nut on one of the two objects, usually welded or glued to the back of said object, and a bolt passing through a hole on the second object in a manner to be engaged by the nut, thereby securing the two objects together.
This arrangement presents many problems, among which, one of the most important is that in the case that one object is hollow, the nut has to be in place at the back of the hollow object before assembling the two objects together. If for any reason the nut is misplaced, and/or if it becomes desirable to introduce a new fastening connection between the two objects, the task of achieving such connection becomes very difficult if not impossible for all practical purposes.
The so-called xe2x80x9cquick nutsxe2x80x9d have also been used to connect two objects. In addition, vibration during the operation of a device, such as an automobile or appliance for example, containing the two objects results very often in loosening of the bolt or xe2x80x9cquick nutxe2x80x9d and in either full disassembling of the objects from each other, or in a vibration noise which is most annoying and often of unacceptable levels. Further, such connections are not water-resistant and water may be easily penetrate the connection point and be transferred from one side of one or both objects to the other side.
Recently, fasteners of the type described in U.S. Pat. No. 4,500,238 (Vassiliou) have been utilized to reduce considerably the potential of bolt or screw loosening and vibration. They have also eliminated the problem of having to place one member of the fastener at the back portion of the hollow object. These fasteners are placed through a slot from the front part of the hollow object. The second part of the fastener, being usually a bolt or a screw, supports the second object by forcing the legs of the fastener (as described for example in U.S. Pat. No. 4,500,238) to open or expand, thereby securing the two objects together. The fasteners of this type have greatly improved the prevailing torque (as defined hereinbelow), as well as the pulling force (as also defined hereinbelow) of the system.
U.S. Pat. No. 2,720,135 (Gisondi), and 5,256,018 (Rattmann et al.) show fasteners of completely different structure than the structure of the fasteners of the instant invention with multiple engagement points. However, the criticality of the crucial positioning of such engagement points is totally non-existent.
Use of tabs at a lower point (further away from the head of the fastener) than the critical range of the present invention, is described in U.S. Pat. No. 5,447,005 (Giannuzzi), regarding an anchor which is intended to be used on hollow walls, plasterboards, etc. Giannuzzi""s tabs are engageable elements, but are not positively engageable elements.
In applications where the anchor is intended to be used on hollow walls, it is very important that the legs, after having been expanded by an expansion member, such as a screw, they expand as much as possible, they resist closing upon applying a pulling force on the screw, and it is easy for an operator to screw or unscrew the expansion member (screw). Giannuzzi improves all these properties for the intended end-use of his anchor, by providing a pair of tabs to the legs of the anchor. These tabs are such, however, that when the anchor is in the wall and fully expanded, the anchor forms (column 5, lines 47-54, and FIG. 7 of Giannuzzi""s disclosure) xe2x80x9ca mechanical truss whose base chords, as shown in FIG. 7, are defined by projecting tabs 15 and 17 pressing into screw 23 and whose side chords are formed by angled blades 12 and 13, the apex of the truss being at head 10xe2x80x9d. In other words, after the legs of the anchor have been expanded by the screw, and the screw has been engaged also to the tabs, the only points of contact of the screw to the anchor are the hole at the head of the anchor and the tabs. This can only be achieved by designing the tabs to have a high enough length in order to further expand the legs in a manner to disengage the initial contact area of the anchor to the screw, through which the initial expansion of the legs occurred, but still have the tabs short enough to permit their engagement to the screw.
The Giannuzzi design increases the pulling force, and decreases considerably the prevailing torque (the toque needed to screw or unscrew the screw into the anchor). Both these changes may be considered as improvements as far as an anchor intended to be used for supporting items on hollow walls are concerned. It is obvious that the increase in pulling force is a definite asset. It is also obvious that the decrease in prevailing torque is a second asset, since the operator can screw and unscrew the screw with considerably less effort, and further taking into account that hollow walls are steady and do not vibrate to render the screw loose, and therefore a high prevailing torque does not offer any advantages. Indeed, a commercial sample of the type disclosed by Giannuzzi, accepting a #6 sheet-metal screw, was examined, and it was found that it was extremely difficult, if at all possible, to turn the screw manually before the screw was engaged to the tabs, while it was excessively easy to turn the screw manually after the screw was engaged to said tabs.
In contrast to the anchors intended to be used on hollow walls, anchors or fasteners intended to be used in parts which are prone to strong vibrations, such as metal sheets supporting plastic parts for example in vehicles for example, the maintenance of an as high as possible prevailing torque is of utmost importance. An anchor as described by Giannuzzi would have detrimental effects with regard to loosening of screws in the case of end-use in the Automotive Industry, on a vehicle for example. The screw would be loosened considerably more easily when the tabs according to Giannuzzi""s teachings were used, than without them. Although the torque required to loosen the screw even further would increase after disengagement from the tabs, this fact would not offer any advantage, since the screw and the part supported by the screw would remain loose anyway.
Since the requirements of the Industry become more and more demanding, fasteners characterized by considerably higher prevailing torque, pulling force, as well as stripping torque than even those disclosed by U.S. Pat. No. 4,500,238 are needed.
One major object of the instant invention is to provide fasteners of highly improved prevailing torque, and/or pulling force, and/or stripping torque without deterioration of any of these properties.
In the following text, the following comments and definitions are appropriate:
The expanding member is preferably a screw having threads and a root on which the threads are supported.
The presence of the positive engagement increases prevailing torque and/or pulling force, and/or stripping torque, without substantially deteriorating any of these properties, as compared to the same fastener lacking said positive engagement.
Prevailing torque is the torque required to render a screw loose.
Pulling force is the pulling force applied on the screw to the point of failure (usually failure occurs an the bents that join the upper side of the head and the lower side of the head).
Stripping torque is the torque required to strip or overcome the engagement of the expanding body or screw to the fastener.
One engagement is commensurate to another engagement if both co-operate, are substantially well aligned with respect to each other, and have the same effect on the screw.
Roughness based on sand paper having a certain number is the roughness given to steel of Rockwell Hardness 70 in the B scale, when sanded by a sand paper having the certain number.
Engageable hole or region is a hole or region which can be engaged with a screw, or similar element.
Non-engageable hole or region is a hole or region which is not suitable to be engaged with a screw, or similar element.
At least partial hole may be a part of a hole, such as an arc for example. However, the hole does not have to be necessarily round.
This invention pertains fasteners comprising:
(a) a substantially flat head portion having an upper side, and a lower side, the upper side having a first engageable hole, the first engageable hole having a first axis, the first axis being substantially perpendicular to the substantially flat head portion;
(b) a neck having an opening and two side neck portions, the neck extending from the lower side of the substantially flat head portion at a substantially right angle with respect to the substantially flat head portion;
(c) two substantially flat legs extending from the neck, each leg having an inner surface, the two inner surfaces of the two legs being at an initial proximity with each other, the legs being expandable in opposite directions upon inserting through and engaging to the first engageable hole an expansion member, thus bringing the expansion member to a contact region of the legs; and
(d) a funnel configuration in the vicinity of the contact region, the funnel being substantially co-axial with the first engageable hole;
wherein any part of the fastener in the range from the lower side of the head to the contact region, including the lower side of the head and the contact region, constitutes a critical secondary body, and wherein at least one portion of the critical secondary body is positively engageable to the expansion member, when the expansion member is inserted through the first engageable hole.
It is critical that the additional engagement is disposed in the range from the lower side of the head to the contact region, including the lower side of the head and the contact region, because if the additional engagement is disposed at a lower point of the fastener (further away from the head), the engagement observed is unacceptable, due to the superiority of an engagement in the range of the instant invention.
At least one positively engageable portion of the critical secondary body may be disposed at the lower side of the head, and/or it may comprise a second engageable hole.
The lower side of the head may comprise an element selected from a group consisting substantially of a lower side extension, a second engageable hole, and a combination thereof, among other configurations.
The first engageable hole is preferably substantially co-axial with the second engageable hole.
The first engageable hole may be disposed in a first impression on the upper side of the head, the first impression having the same direction as a second impression on the lower side of the head, in which second impression the second engageable at least partial hole is disposed. Alternatively, the first engageable hole may be disposed in a first impression on the upper side of the head, the first impression having an opposite direction as a second impression on the lower side of the head, in which second impression the second engageable at least partial hole is disposed.
The at least one positively engageable portion of the critical secondary body may also be disposed at the opening. In such a case, it preferably comprises at least one rib. More preferably, it comprises at least a pair of ribs, one rib being disposed over each leg.
The at least one positively engageable portion of the critical secondary body may also be disposed at the neck, preferably in the form of threading teeth.
Further, the at least one positively engageable portion of the critical secondary body may be disposed at the funnel. In such a case, the funnel may preferably comprise an element selected from a group substantially consisting of a slit, a groove, a shoulder, a rib, a tab, a surface roughness higher than that of sandpaper #300, and a combination thereof.
Also, the at least one positively engageable portion of the critical secondary body may be disposed at the contact region. Again, in such a case, the contact region preferably may comprise an element selected from a group substantially consisting of a slit, a groove, a shoulder, a rib, a tab, a surface roughness higher than that of sandpaper #300, and a combination thereof.
The engagement of the critical secondary body may be at least partially commensurate or at least non-commensurate to the first engageable hole.
The upper side of the head and the lower side of the head of the fastener of the instant invention may be substantially in contact or separated by a gap, depending on the application.
Also, when water-proofing, and/or gas-proofing are desired for a particular application, and/or vibration noises are to be prevented, an elastic body is preferably integrally molded at least at the lower side of the substantially flat head portion. Such elastic bodies are for example disclosed in U.S. Pat. No. 5,725,343, provisional patent application No. 60/170,112, filed Dec. 10, 1999, and patent application No. Ser. 09/561,505 filed Apr. 28, 2000, all of which are incorporated herein by reference.
The instant invention also pertains vehicles comprising parts connected with the fasteners described above.